The invention generally relates to a formation isolation valve.
A formation isolation valve may be located downhole to form a sealed access to a particular formation. In this manner, the formation isolation valve may be opened or run open so that a tubular string may be run downhole through the valve to permit the string to perform one or more downhole functions below the formation isolation valve. After these functions are complete, the string may be retrieved. After the end of the string passes through the valve during the retrieval of the string, the valve may then be operated to seal off the formation below the valve. In this manner, a shifting tool may be located at the end of the tool to physically engage the valve to cause the valve to close. The shifting tool may also be used to open the valve.
As an example, the string may include a gravel packing tool to route gravel into an annular region that surrounds a screened portion of a production tubing of the well. In this manner, the gravel travels down a central passageway of the string and through radial ports of the gravel packing tool into the annular region. The gravel may include sand that falls between the interior opening of the formation isolation valve and the outside of the string to create friction between the string and the valve. Unfortunately, the friction between the string and valve may cause the string to unintentionally physically engage the valve to cause the valve to prematurely close on the string. Thus, such a scenario may cause the string to become wedged in the valve.
Thus, there is a continuing need for an arrangement that addresses one or more of the problems that are stated above.
In an embodiment of the invention, an assembly that is usable in a subterranean well includes a valve, a sleeve and an index mechanism. The valve is adapted to selectively isolate a region of the well, and the sleeve is adapted to be moved by a downhole tool to cause the valve to transition from a first state to a second state. The index mechanism prevents the valve from transitioning from the first state to the second state until after a position of the sleeve follows a predefined pattern.